Cobalt, a metallic element of the iron group. It resembles iron in appearance, but has a slight reddish tinge. Cobalt is harder than iron, but melts at a lower temperature and is somewhat heavier. Acids will dissolve cobalt.

Cobalt is very resistant to corrosion and wear, even at high temperatures. For this reason, alloys containing cobalt are used for making jet engine and gas turbine parts. Cobalt alloyed with chromium and tungsten is used in making high-speed cutting tools. Cobalt has magnetic properties that make it suitable for alloys used to make strong permanent magnets. An important example is alnico, an alloy containing aluminum, nickel, iron, and cobalt.

Cobalt is required in tiny amounts for proper nutrition. The element forms an essential part of Vitamin B12.

Cobalt 60, a radioactive isotope, is used as a commercial source of high-energy radiation. In medicine, the radiation is used to destroy cancerous tissue. In industry, it can be used to detect flaws in metal parts.

Various compounds of cobalt are used as pigments in pottery, glass, enamels, and paints. One of the best known is cobalt blue, a bluish-green compound of alumina and cobalt oxide that has long been used in pottery. Some cobalt compounds are used as driers, substances that promote drying in paints, varnishes, and printing inks.

Cobalt was discovered by Georg Brandt, a Swedish chemist, about 1735. Cobalt is not found in a pure state in nature, but it often occurs with nickel, copper, or iron. Most cobalt is obtained as a by-product in smelting nickel or copper ores. A variety of metallurgical processes are used to recover the cobalt, depending on the type of ore. Zambia, Canada, Australia, and Russia are the world's leading producers of cobalt.

Symbol: Co Atomic number: 27. Atomic weight: 58.9332. Melting point: 2,723F. (1,495 C.). Boiling point: 5,198 F. (2,870 C.). Specific gravity: 8.9. Cobalt belongs to Group VIII of the Periodic Table and has a valence of +2 or +3.